Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $112.75   11.747%   $125.9947   $125.99   $126.00   $126.00  
  Purchase #2 $192.46   9.693%   $211.1151   $211.12   $211.10   $211.10  
  Purchase #3 $204.71   5.362%   $215.6866   $215.69   $215.70   $215.70  
  Purchase #4 $86.84   7.743%   $93.564   $93.56   $93.55   $93.60  
  Purchase #5 $32.39   11.265%   $36.0387   $36.04   $36.05   $36.00  
  Purchase #6 $41.45   7.783%   $44.6761   $44.68   $44.70   $44.70  
  Purchase #7 $34.42   3.384%   $35.5848   $35.58   $35.60   $35.60  
  7 purchase totals = $705.02       $762.6600   $762.66   $762.70   $762.70